Simplify the following expression: $p = \dfrac{7z}{4} + \dfrac{z}{9}$
Solution: In order to add expressions, they must have a common denominator. The smallest common denominator is the least common multiple of $4$ and $9$ $\lcm(4, 9) = 36$ $ p = \dfrac{9}{9} \cdot \dfrac{7z}{4} + \dfrac{4}{4} \cdot \dfrac{z}{9} $ $p = \dfrac{63z}{36} + \dfrac{4z}{36}$ $p = \dfrac{63z +4z}{36}$ $p = \dfrac{67z}{36}$